Concrete structures, particularly highways and bridges, typically utilize metallic reinforcement members embedded therewithin to provide stability and additional strength to the concrete, as well as to enhance the ability of the concrete to withstand shear forces. These reinforcements are used in a variety of configurations, and are typically present in the form of reinforcing rods, wire mesh, metallic fibers, and the like. Reinforcements are usually situated within the cured concrete by pouring raw or uncured concrete therearound or, in the case of metallic fibers, added during the concrete mixing operation for subsequent curing. The term “raw concrete” is utilized herein in a comprehensive sense, and is intended to relate to wet workable concrete mixtures which have not yet cured to their solid form.
Upon the passage of time, the metallic reinforcements have a tendency to corrode as external elements including moisture and pollutants such as carbon dioxide, oxides of sulfur, oxides of nitrogen, hydrogen sulfide, and road treatment chemicals permeate along and through the concrete structure and reach the surface of the metal reinforcement. When utilized, for example, in highways, bridges, and parking structures, chlorides including sodium chloride and calcium chloride may permeate the concrete structure due to the widespread utilization of such materials as a mechanism to melt ice and snow from the road surfaces. Both calcium chloride and sodium chloride are widely used for this purpose, and their use, although necessary for safety reasons, has been linked to the rapid deterioration of certain concrete structures.
A characteristic of common concrete mixtures that exacerbates corrosion of, for example, metallic elements embedded within a mass of concrete is alkaline silica reactivity (ASR), a condition in which alkali in cement attacks silica-based aggregates to form gels that can absorb water. Such water absorption can lead to crack formation in the concrete mass due to freeze-thaw cycles, as well as the reception and retention of moisture adjacent to metallic elements that may corrode in the presents of water. One approach to reduce and/or eliminate the alkaline silica reactivity in concrete admixtures is through the use of lithium salts such as lithium nitrate to neutralize the silica found in common concrete admixture recipes. An example of the use of lithium salts to thwart alkaline silica reactivity in concrete mixtures is found in WO 04044267 published in the name of the Virginia Transportation Research Counsel. Though the use of lithium salts has proven to be beneficial in minimizing alkaline silica reactivity in concrete mixtures, such utility alone does not provide a total preventative and/or restorative corrosion protection solution for corrosion-susceptible elements disposed in concrete mixtures.
In order to facilitate the access of corrosion inhibiting materials to concrete reinforcements, it is normally desirable for such materials to be added to the raw concrete mixture in order to provide for contact with the surfaces of the metallic reinforcement members or structures prior to concrete curing. The corrosion inhibiting materials added in this fashion normally migrate throughout the concrete mixture at a rate sufficient to provide ongoing protection over relatively extended periods of time, and hence have the ability to protect the metallic reinforcements over such extended periods of time.
In other embodiments however, such corrosion inhibiting materials need to be applied to cured concrete structures having corrosion-susceptible reinforcements encased therewithin. As such, the corrosion inhibiting materials are preferably applied to the surface of the concrete structure and thereafter migrate inwardly to protect the surface of the metallic reinforcements.
As a further aspect of corrosion inhibiting materials, it is a common objective to utilize ecologically friendly components wherever possible. In this connection, the formulation of the present invention preferably provides for the use of ecologically friendly materials, and thus the goals and objectives of inhibiting corrosion in large structures can be undertaken without significantly contributing to the release of ecologically harmful products into the environment.
In view of the above, it is therefore a principal object of the present invention to provide a corrosion inhibiting composition that may be applied to raw or cured concrete mixtures for protecting corrosion-susceptible elements disposed within such concrete mixtures, with the corrosion inhibiting composition incorporating one or more alkaline silica reactivity suppression agents and one or more corrosion inhibiting agents.
It is a further object of the present invention to provide a corrosion inhibiting composition having the capability to migrate within cured concrete mixtures along the surface of embedded corrosion-susceptible elements so as to provide corrosion protection thereto over a prolonged period of time.
It is a further object of the present invention to provide a corrosion inhibiting composition comprising ecologically friendly components.
It is a still further object of the present invention to provide a corrosion inhibiting composition for protection of metallic reinforcements embedded within concrete mixtures without adversely affecting the curing rate or ultimate strength of the respective concrete mixtures.
Other objects of the present invention will become apparent to those skilled in the art upon a study of the following specification and appended claims.